(a) Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for forming a bonding pad of a semiconductor device.
(b) Description of the Related Art
Generally, a bonding pad functions as a terminal which connects a semiconductor device with its package. After packaging the semiconductor device including the bonding pad exposing some portions of a top metal line of the device, portions being used as a pin are mutually connected through the bonding works. These bonding works realize the connection of the metal line in the device with the outer power supply.
For good result of the bonding works, it is required that there is no impurities or oxide layer on the surface of the bonding pad.
U.S. Pat. Nos. 6,006,764 and 6,355,576 disclose a conventional bonding pad structure for superior adhesion.
FIG. 1 is a cross-sectional view of a conventional bonding pad of a semiconductor device. With reference to FIG. 1, a lower insulating layer 2 such as oxide layer is formed on a structure 1 of a semiconductor substrate, which includes individual devices over a semiconductor substrate or a lower metal line over a semiconductor substrate.
A top metal line 3 which is formed of Al or Cu is formed on the lower insulating layer 2.
An upper insulating layer 4 is formed on the top metal line 3 and the lower insulating layer 2. Portions of the upper insulating layer 4 are etched to form a bonding pad 100 which exposes portions of the top metal line 3.
After forming the bonding pad 100 as described above, O2 treatment to remove impurities from the exposed surface of the top metal line 3 is performed, and then wire bonding process is performed.
In wire bonding process, pre-cleaning process is usually performed before the bonding work.
Even though the O2 treatment and the pre-cleaning process is performed, the exposed surface of the top metal line 3 reacts with oxygen in atmosphere to form oxide layer 5 of Al2O3.
Due to the Al2O3, adhesion strength of the solder in wire bonding becomes weak and the bonding is poor. In order to restore the bonding, re-working of the bonding pad is required, and therefore, manufacturing cost become high and productivity becomes deteriorated.